Attempts to distinguish different "species of motoneurons will be continued and extended, using such electrophysiological properties as firing rate, fatigability, and critical firing level to define types of motoneurons. Further work will be carried out to test the tentative conclusions reached in current studies that input is distributed with equal density to all the members of a pool. Efforts to develop improved electromyographic techniques will also be continued, so that the results of animal studies can be applied directly to human disease.